Various optical scanning apparatus have been developed to read and decode optical indicia, such bar as code symbols on a target such as a label. While early bar code scanners were designed to read symbols at a relatively close distance, there exists a need to read symbols at greater and greater distances, for example in warehousing environments. Conventional optical scanning systems, such as hand-held bar code laser scanners, typically have a limited working range due to the constraints imposed on the optical assembly. Motorized systems with additional lenses or mirrors have been developed to re-position the laser beam waist relative to the fixed lens assembly, thereby increasing the working range of the scanning apparatus, but such improvements are complicated and add cost.
Decoding images has always proved challenging, in part because decoding systems work best with a sharp representation of the bar code symbol, and a sharp representation is not always possible. Due to optical, environmental or physical factors, the representation may be out of focus, too close to the reader, or too far away from the reader. One solution to this problem is to manually move the symbol to a range within the capability of the reader, either by moving the scanning apparatus or by moving the target. This solution can be cumbersome, frustrating, or may not even be possible. Various systems have been developed to aide in focusing the laser on the target, such as ranging systems to determine the distance from the reader to the target, but these systems add complexity and cost.